diff --git a/samples/Samples.Mvc5/Controllers/HomeController.cs b/samples/Samples.Mvc5/Controllers/HomeController.cs
index a176a204a..bb6a45224 100644
--- a/samples/Samples.Mvc5/Controllers/HomeController.cs
+++ b/samples/Samples.Mvc5/Controllers/HomeController.cs
@@ -10,6 +10,8 @@
 using Samples.Mvc5.EfModelFirst;
 using Samples.Mvc5.EFCodeFirst;
 using Samples.Mvc5.Helpers;
+using System.Threading.Tasks;
+using System.Collections.Generic;
 
 namespace Samples.Mvc5.Controllers
 {
@@ -131,6 +133,34 @@ public ActionResult About()
         /// <returns>The <see cref="ActionResult"/>.</returns>
         public ActionResult ResultsAuthorization() => View();
 
+        public async Task<ActionResult> CallAsync()
+        {
+            var profiler = MiniProfiler.Current;
+            var service = new FooService();
+            using (profiler.Step("action"))
+            {
+                var head = profiler.Head;
+                var tasks = new List<Task>();
+                for (int i = 0; i < 10; i++)
+                {
+                    tasks.Add(service.FooAsync(head));
+                }
+                await Task.WhenAll(tasks);
+                return Content("All good");
+            }
+        }
+
+        class FooService
+        {
+            public async Task FooAsync(Timing head)
+            {
+                using (new Timing(MiniProfiler.Current, head, "foo async", minSaveMs: 100000))
+                {
+                    await Task.Delay(100).ConfigureAwait(false);
+                }
+            }
+        }
+
         /// <summary>
         /// fetch the route hits.
         /// </summary>
diff --git a/samples/Samples.Mvc5/Views/Home/Index.cshtml b/samples/Samples.Mvc5/Views/Home/Index.cshtml
index 3eb0a9b5e..b40fea6f6 100644
--- a/samples/Samples.Mvc5/Views/Home/Index.cshtml
+++ b/samples/Samples.Mvc5/Views/Home/Index.cshtml
@@ -65,6 +65,7 @@
                 <li><a href="/Home/MassiveNesting2">Massive Nesting 2</a></li>
                 <li><a href="/Home/ParameterizedSqlWithEnums">Parameterized SQL with Enums</a></li>
                 <li><a href="/Home/MinSaveMs">Test Min Save Ms</a></li>
+                <li><a href="/Home/CallAsync">Async call + Concurrency</a></li>
             </ul>
         </div>
     </div>
diff --git a/src/MiniProfiler.Shared/Timing.cs b/src/MiniProfiler.Shared/Timing.cs
index e3aa9839f..64d8c6a48 100644
--- a/src/MiniProfiler.Shared/Timing.cs
+++ b/src/MiniProfiler.Shared/Timing.cs
@@ -3,6 +3,8 @@
 using System.Linq;
 using System.Runtime.Serialization;
 using StackExchange.Profiling.Helpers;
+using System.Threading;
+using System.Threading.Tasks;
 #if NET45
 using System.Web.Script.Serialization;
 #endif
@@ -22,6 +24,9 @@ public class Timing : IDisposable
         private readonly decimal? _minSaveMs;
         private readonly bool _includeChildrenWithMinSave;
 
+        // used for concurrent access detection
+        private int _threadsAccessing = 0;
+
         /// <summary>
         /// Initialises a new instance of the <see cref="Timing"/> class. 
         /// Obsolete - used for serialization.
@@ -253,19 +258,43 @@ public void Stop()
         /// </remarks>
         public void AddChild(Timing timing)
         {
-            if (Children == null)
+            if (Interlocked.Increment(ref _threadsAccessing) > 1)
+                throw new Exception("Concurrent access");
+
+            try
+            {
+                if (Children == null)
                 Children = new List<Timing>();
 
-            Children.Add(timing);
-            if(timing.Profiler == null)
-                timing.Profiler = Profiler;
-            timing.ParentTiming = this;
-            timing.ParentTimingId = Id;
-            if (Profiler != null)
-                timing.MiniProfilerId = Profiler.Id;
+                Children.Add(timing);
+                if(timing.Profiler == null)
+                    timing.Profiler = Profiler;
+                timing.ParentTiming = this;
+                timing.ParentTimingId = Id;
+                if (Profiler != null)
+                    timing.MiniProfilerId = Profiler.Id;
+            }
+            finally
+            {
+                Interlocked.Decrement(ref _threadsAccessing);
+            }
         }
 
-        internal void RemoveChild(Timing timing) => Children?.Remove(timing);
+        internal void RemoveChild(Timing timing)
+        {
+            if (Interlocked.Increment(ref _threadsAccessing) > 1)
+                throw new Exception("Concurrent access");
+
+            Task.Delay(10).Wait();
+            try
+            {
+                Children?.Remove(timing);
+            }
+            finally
+            {
+                Interlocked.Decrement(ref _threadsAccessing);
+            }
+        }
 
         /// <summary>
         /// Adds <paramref name="customTiming"/> to this <see cref="Timing"/> step's dictionary of